title: Immunomodulating effects of environmentally realistic copper concentrations in Mytilus edulis adapted to naturally low salinities.
abstract: The monitoring of organisms' health conditions by the assessment of their immunocompetence may serve as an important criterion for the achievement of the Good Environmental Status (GES) as defined in the Marine Strategy Framework Directive (EU). In this context, the complex role of natural environmental stressors, e.g. salinity, and interfering or superimposing effects of anthropogenic chemicals, should be carefully considered, especially in scenarios of low to moderate contamination. Organisms from the Baltic Sea have adapted to the ambient salinity regime, however energetically costly osmoregulating processes may have an impact on the capability to respond to additional stress such as contamination. The assessment of multiple stressors, encompassing natural and anthropogenic factors, influencing an organisms' health was the main aim of the present study. Immune responses of Mytilus edulis, collected and kept at natural salinities of 12‰ (LS) and 20‰ (MS), respectively, were compared after short-term exposure (1, 7 and 13 days) to low copper concentrations (5, 9 and 16 μg/L Cu). A significant interaction of salinity and copper exposure was observed in copper accumulation. LS mussels accumulated markedly more copper than MS mussels. No combined effects were detected in cellular responses. Bacterial clearance was mostly achieved by phagocytosis, as revealed by a strong positive correlation between bacterial counts and phagocytic activity, which was particularly pronounced in LS mussels. MS mussels, on the other hand, seemingly accomplished bacterial clearance by employing additional humoral factors (16 μg/L Cu). The greatest separating factor in the PCA biplot between LS and MS mussels was the proportion of granulocytes and hyalinocytes while functional parameters (phagocytic activity and bacterial clearance) were hardly affected by salinity, but rather by copper exposure. In conclusion, immune responses of the blue mussel may be suitable and sensitive biomarkers for the assessment of ecosystem health in brackish waters (10-20‰S).
authors.affiliation: Alfred Wegener Institute for Polar and Marine Research, Am Handelshafen 12, 27570 Bremerhaven, Germany. nicole.hoeher@awi.de
authors.forename: Nicole
authors.initials: N
authors.lastname: Höher
authors.forename: Francesco
authors.initials: F
authors.lastname: Regoli
authors.forename: Awantha
authors.initials: A
authors.lastname: Dissanayake
authors.forename: Matthias
authors.initials: M
authors.lastname: Nagel
authors.forename: Michael
authors.initials: M
authors.lastname: Kriews
authors.forename: Angela
authors.initials: A
authors.lastname: Köhler
authors.forename: Katja
authors.initials: K
authors.lastname: Broeg
mesh_terms: D000818:Animals; D018407:Bacterial Physiological Phenomena; D020169:Caspases / Q000378:metabolism; D003300:Copper / Q000378:metabolism / Q000633:toxicity*; D004789:Enzyme Activation / Q000187:drug effects; D005880:Gills / Q000187:drug effects; D006434:Hemocytes / Q000166:cytology / Q000187:drug effects; D056747:Immunomodulation / Q000187:drug effects; D016014:Linear Models; D049880:Mytilus edulis / Q000187:drug effects* / Q000201:enzymology / Q000276:immunology / Q000382:microbiology; D010587:Phagocytosis / Q000187:drug effects; D025341:Principal Component Analysis; D054712:Salinity; D012623:Seawater / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D014874:Water Pollutants, Chemical; D003300:Copper; D020169:Caspases
keywords: Baltic Sea; Brackish waters; Copper; Immune responses; Multiple stressors; Mytilus; Salinity